The field of the invention is polyamide adhesives for textiles and the invention is particularly concerned with powdered copolyester amides for heat sealing textiles.
The state of the art of methods and apparatus for depositing powdered thermoplastic adhesive materials on the outer surface to textiles may be ascertained by reference to U.S. Pat. Nos. 4,139,613; 4,183,978; 3,667,422; 4,368,090; 4,459,389; and 4,487,895; and British Patent No. 1,295,558, the disclosures of which are incorporated herein by reference.
Copolyester amides useful as adhesives and the state of the art thereof may be ascertained by reference to U.S. Pat. Nos. 3,849,514; 4,101,524; 4,217,435; 4,219,458; 4,222,976; 4,376,194, and 4,433,117 the disclosures of which are incorporated herein by reference.
The state of the prior art of producing polyamide powders may be ascertained by reference to the Kirk-Othmer "Encyclopedia of Chemical Technology", 2nd Ed., Vol. 16 (1968) under the section "polyamide (plastics)", pages 88-105, particularly page 92, polylauryllactam (nylon-12), and polyundecanamide (nylon-11), page 101, Solution Processes, and Powder Processing, pages 101-102, the disclosures of which are incorporated herein.
According to British Patent No. 1,295,558, the spot coating of interlinings for textiles is carried out mainly by three methods:
1. A suitable plastic powder, for example, a polyamide or polyethylene based powder, is applied by a doctor blade to an engraving roller having recesses in the form of dots disposed in an even raster or grid formation and having a diameter of about 1 mm so that the plastic powder fills the recesses. The web of the interlining, which has been preheated to a high temperature by means of heating rollers, is passed around the engraving roller under tension and the plastics powder is transferred from the recesses to the web of interlining material (Powder point or powder dot process).
2. A network of spots of a suitable plastic, such as polyethylene, is prepared in the form of a raster, the spots being interconnected by very fine webs. The network is applied dry to the hot interlining, the fine webs breaking up and disappearing, and the spots of the plastic fusing to the interlining. Interlinings of this kind have a relatively hard handle and can be fixed only on relatively heavy facing materials and the plastics also tend to bleed through and stick to the fixing press.
3. In the least expensive and least complex process, suitable plastics, such as PVC, polyamide or polyethylene, are mixed with plasticizers or in aqueous or solvent-containing media to form pastes which are printed by means of a printing roller formed with perforations arranged as a raster (paste printing process).
The use of copolyester amides as thermoplastic adhesives is known. Depending on their composition and the type of manufacture, these copolyester amides differ so much in their properties that they must be improved when used as thermoplastic adhesives for textiles.
Thermoplastic adhesives for textiles and containing polyester amides prepared by the method of U.S. Pat. No. 4,101,524 suffer from the drawback that lactam splitting is carried out hydrolytically under pressure, not acidolytically. The polyamide blocks have low sequence lengths, M.sub.n &lt;1,000, whereby the melting points are lowered for equal polyamide proportions. Randomly distributed polyester amides are present. These polyester amides are only inadequately resistant to cleaning. Lastly the polyester amides of this state of the art definitely do not contain butanediol, and also they differ in the manner of their preparation because in this state of the art a polyamide technique is used, not a polyester technique.
U.S. Pat. No. 3,849,514 discloses how to prepare block copolyester amides starting from oligoamides having terminal ester and hydroxyester groups and oligopolyesters with terminal hydroxy groups. The application of such block copolyester amides as thermoplastic adhesives is also recommended. However, due to their high melting point, they are unsuitable as thermoplastic adhesives for textiles. Furthermore, such products have two melting points, and when at all suitable as thermoplastic adhesives, they can only be processed with difficulty. Moreover they entail a costly manufacturing procedure due to the use of diamines.
U.S. Pat. No. 4,433,117 discloses block copolyester amides containing piperazine and aromatic dicarboxylic acids such as terephthalic acid in the polyamide block and again terephthalic acid as dicarboxylic acid in the polyestcr block. Again, these thermoplastic adhesives are unsuitable as thermoplastic adhesives for textiles due to their high melting points.
The copolyester amide molding materials described in U.S. Pat. Nos. 4,219,458 and 4,222,976, aside from having high melting points above 150.degree. C., also necessarily contain aluminum powder and glass fibers. Such mixtures cannot be used as thermoplastic adhesives for textiles because the high bonding temperatures thermally damage the fabrics.
U.S. Pat. No. 4,217,435 discloses mixtures of polyesters and polyamides used as thermoplastic adhesives. The mixtures are obtained from mixtures of melts. The conventionally prepared melt thermoplastic adhesives from those mixtures evince properties different from those of copolyester amides of comparable compositions. Therefore the disclosure of this patent cannot contribute to the development of selected copolyester amides as thermoplastic adhesives for textiles.
U.S. Pat. No. 4,376,194 discloses polyester amides containing benzene dicarboxylic acids and 1,4-butanediol in the polyester portion and omega-undecanoic- and omega-dodecanoic-acid parts, respectively in the polyamide portion. In the method of this patent, the polyamide components are used as monomers, whereby these components are randomly distributed in the polyester amides so made. When used as thermoplastic adhesives for textiles, these products evince inadequate resistance to chemical cleaning. They also differ in that they contain no hexanediol and, therefore, they are adhesive and less crystalline and, accordingly, cannot be used in the powder point process disclosed in British Patent No. 1,295,558. Compared with the block copolyester amides of the present invention, randomly distributed copolyester amides show lesser resistance to cleaning for equal polyamide portions.